The present invention relates to a gyroscopic sensor comprising:
a sensitive element suitable designed to vibrate;
an electrode carrier capable of carrying excitation electrodes and detection electrodes for detecting the vibration of the sensitive element; and
elements for supporting the electrode carrier.
The elements for supporting the electrode carrier comprise a base and a decoupling element interposed between the base and the electrode carrier. The decoupling element is designed to decouple the electrode carrier and the sensitive element relative to the dimensional variations of the base that are brought about by the thermal variations to which the sensor is subjected. For example, it comprises support rods for the electrode carrier that are designed to pass right through the base in order to transport signals between the electrodes and an electronic circuit, as described in patent application FR 2 805 039.
Such a sensor is generally fastened to a support, called an inertial core. This inertial core is then integrated into an inertial measurement system with which a carrier, liable to vibrate or receive a shock, is equipped. Since the sensor is firmly attached to the inertial core, it may undergo these vibrations during use of the carrier. The sensitive element vibration modes induced by the vibrations of the carrier are hereafter named parasitic vibration modes.
In order not to amplify the vibrations coming from the carrier, the base of such a sensor is generally made of a stiff material. For example, the base is a metal plate 10 mm in thickness having a mass of about 70 g. Therefore, the inertial sensor is heavy and bulky.
The inertial information relative is included in a frequency range of one hundred Hertz, located on both sides of the vibratory resonance frequency of the gyroscope sensor. The inertial information comprises information relative to the angle of rotation or to the rotation speed of the gyroscopic sensor's carrier. The vibratory resonance frequency of the gyroscope sensor is hereafter named “useful” vibration mode. The interferences between the mechanical parasitic vibration modes and the “useful” vibration mode damage the performance of the gyroscopic sensor.
To guaranty optimal performance of the gyroscopic sensor, it is desirable to provide a gyroscope sensor having a first parasitic vibration mode situated far from the “useful” vibration mode.